docs: def get_url(self, fname):
          """
          Get the full URL to download a file in the registry.
  
          Parameters
          ----------
          fname : str
              The file name (relative to the *base_url* of the remote data storage) to
              fetch from the local storage.
  
          """
          self._assert_file_in_registry(fname)
          return self.urls.get(fname, "".join([self.base_url, fname]))